I highly recommend you don't do this. Use a ORACLE TRIGGER instead. Why?

It doesn't matter what process inserts into your target table, the table owns the task of fetching the sequence value.
Your Informatica sequence generator will be out of sync in each environment and this will cause you headaches with data replication (DEV/TST/PRD) and code replication. Yes, Informatica handles migration of sequence generators better now than in the past, but it's still easy to break.
Use Informatica Sequence generators ONLY if you are resetting it each run.

I suppose that there are two different target table (different database)